diff --git a/fin_defs/__init__.py b/fin_defs/__init__.py
index 6f8286e..dc716c4 100644
--- a/fin_defs/__init__.py
+++ b/fin_defs/__init__.py
@@ -505,6 +505,11 @@ class AssetInformation:
 
 THREE_DECIMALS_UNDER_THIS_AMOUNT = 0.10
 
+def assert_same_asset(do: str, a_asset: 'AssetAmount', b_asset: 'AssetAmount'):
+    if a_asset.asset != b_asset.asset:
+        msg = f'Attempting to {do} {a_asset} and {b_asset}, but these must have the same asset'
+        raise ValueError(msg)
+
 
 @enforce_typing.enforce_types
 @dataclasses.dataclass(frozen=True, eq=True, slots=True)
@@ -547,11 +552,7 @@ class AssetAmount:
             return other
         if other.is_zero():
             return self
-        if self.asset != other.asset:
-            msg = (
-                f'AssetAmount must have same asset, but: {self.asset} != {other.asset}'
-            )
-            raise ValueError(msg)
+        assert_same_asset('add', self, other)
 
         return AssetAmount(self.asset, self.amount + other.amount)
 
@@ -564,18 +565,13 @@ class AssetAmount:
             return -other
         if other.is_zero():
             return self
-        if self.asset != other.asset:
-            msg = (
-                f'AssetAmount must have same asset, but: {self.asset} != {other.asset}'
-            )
-            raise ValueError(msg)
+        assert_same_asset('subtract', self, other)
         return AssetAmount(self.asset, self.amount - other.amount)
 
+
     def __truediv__(self, other: 'Decimal | AssetAmount') -> 'Decimal | AssetAmount':
         if isinstance(other, AssetAmount):
-            if self.asset != other.asset:
-                msg = f'Attempting to divide {self} by {other}, but these must have the same asset'
-                raise ValueError(msg)
+            assert_same_asset('divide', self, other)
             return self.amount / other.amount
         return AssetAmount(self.asset, self.amount / other)
 
@@ -588,11 +584,7 @@ class AssetAmount:
             raise TypeError(msg)
         if self.is_zero() or other.is_zero():
             return self.amount - other.amount
-        if self.asset != other.asset:
-            msg = (
-                f'AssetAmount must have same asset, but: {self.asset} != {other.asset}'
-            )
-            raise ValueError(msg)
+        assert_same_asset('compare', self, other)
         return self.amount - other.amount
 
     def is_zero(self) -> bool:
diff --git a/test/test_asset_amount.py b/test/test_asset_amount.py
index 5c24961..6c988a6 100644
--- a/test/test_asset_amount.py
+++ b/test/test_asset_amount.py
@@ -1,4 +1,5 @@
 from decimal import Decimal
+import re
 
 import pytest
 
@@ -83,7 +84,7 @@ def test_add_wrong_type():
 def test_add_wrong_asset():
     with pytest.raises(
         ValueError,
-        match='AssetAmount must have same asset, but: fiat:USD != fiat:DKK',
+        match=re.escape('Attempting to add $20.00 USD and 21.00 DKK, but these must have the same asset'),
     ):
         assert USD_20 + DKK_21
 
@@ -96,7 +97,7 @@ def test_sub_wrong_type():
 def test_sub_wrong_asset():
     with pytest.raises(
         ValueError,
-        match='AssetAmount must have same asset, but: fiat:USD != fiat:DKK',
+        match=re.escape('Attempting to subtract $20.00 USD and 21.00 DKK, but these must have the same asset'),
     ):
         assert USD_20 - DKK_21
 
@@ -109,7 +110,7 @@ def test_cmp_wrong_type():
 def test_cmp_wrong_asset():
     with pytest.raises(
         ValueError,
-        match='AssetAmount must have same asset, but: fiat:USD != fiat:DKK',
+        match=re.escape('Attempting to compare $20.00 USD and 21.00 DKK, but these must have the same asset'),
     ):
         assert USD_20 < DKK_21
 
@@ -117,6 +118,6 @@ def test_cmp_wrong_asset():
 def test_div_wrong_asset():
     with pytest.raises(
         ValueError,
-        match='AssetAmount must have same asset, but: fiat:USD != fiat:DKK',
+        match=re.escape('Attempting to divide $21.00 USD and 21.00 DKK, but these must have the same asset'),
     ):
         assert USD_21 / DKK_21